The culling of mixed mail pieces into discrete categories is an essential step in the processing of mail to its ultimate destination. Accordingly, the mechanization of mail culling has been an ongoing project for many years. Much of the effort has been concentrated on producing an output flow of machinable letter mail. The equipment which has been developed uses various techniques to cull out those mail pieces which, because of various dimensions such as overall size, thickness, or weight, are outside the predetermined limits of machinable letter dimensions. The latter mail pieces are identified generally as flats, parcels, rolls, etc. Unfortunately, the flats removed by present day processes are culled out at different locations for various reasons. For example, the gaging roller technique culls mail pieces which exceed the 1/4-inch letter mail thickness. The material culled by this process includes slugs (mail pieces of irregular dimensions which preclude the stacking thereof one upon the other), small parcels, rolls and flats which are thicker than 1/4-inch. Another widely used technique is the flats extractor which removes mail pieces which exceed a certain height. These mail pieces include flats which are generally under 1/4-inch thick and letter size mail standing on end. A third technique which has been utilized is air-culling in which documents are removed from the mail stream when they exceed a predetermined weight-to-surface area ratio. The material removed by this last technique is a mixture of heavy flats, slugs, small parcels and rolls. It will be noted that in the aforementioned examples, the flats have been culled at three different locations and have been mixed with non-machinable mail pieces. The recovery of the machinable flats involves considerable time and labor which would have been eliminated had a single output of machinable flats been provided during the culling process.
In achieving the last mentioned goal, it should be noted that the variation of flat mail size and weight greatly compounds the difficulty of using existing letter size mail processing techniques. Also collection mail may contain items which are extremely difficult to handle by automated equipment. What is required to handle the variability of mail pieces is equipment of relatively simple low-velocity open construction which will be inherently free from hard jams and mail damage. The system of the present invention fills such a need.